Prostaglandin D2(PGD2) is a metabolic product of arachidonic acid through PGG2 and PGH2, and known to have various potent physiological activities. For example, in non-patent literature 1 it is described that PGD2 is involved in sleeping and secretion of hormones in central nervous system, and in inhibiting activity of platelet aggregation, contraction of bronchial smooth muscle, vasodilation and constriction of a blood vessel etc. in peripheral system. Moreover, PGD2 is considered to be involved in forming pathological condition of an allergic disease such as bronchial asthma since it is a major metabolic product of arachidonic acid produced from a mast cell, and has a potent bronchoconstricting effect, causing an increase of vascular permeability and migration of inflammatory cell such as eosinophils.
A DP receptor (also called DP1 receptor) or CRTH2 receptor (also called DP2 receptor) is known as a receptor of PGD2 but these are completely different receptors. In Patent literatures 1-10 indole derivatives having a DP receptor antagonistic activity is disclosed, and in Patent literatures 11-15 indole derivatives having a CRTH2 receptor-antagonistic activity is disclosed
Also, indole derivatives having inhibitory activity against noradrenalin re-uptake are disclosed in Patent literature 16.    Patent literature 1: WO 2001/079169 Pamphlet    Patent literature 2: WO 2002/094830 Pamphlet    Patent literature 3: WO 2003/062200 Pamphlet    Patent literature 4: WO 2004/039807 Pamphlet    Patent literature 5: WO 2004/103970 Pamphlet    Patent literature 6: WO 2004/111047 Pamphlet    Patent literature 7: WO 2005/056527 Pamphlet    Patent literature 8: WO 2003/022813 Pamphlet    Patent literature 9: WO 2003/022814 Pamphlet    Patent literature 10: WO 2004/078719 Pamphlet    Patent literature 11: WO 2003/097598 Pamphlet    Patent literature 12: WO 2003/066046 Pamphlet    Patent literature 13: WO 2003/066047 Pamphlet    Patent literature 14: WO 2005/040112 Pamphlet    Patent literature 15: GB 2407318 Pamphlet    Patent literature 16: WO 2005/019208 Pamphlet    Non-patent literature 1: Pharmacol. Review, Vol. 46, page 205-229 (1994)    Non-patent literature 2: Pharmaco., Vol. 55 (1), page 56-64 (2000)